ORALS

Technologies are getting more complex each day and with that the metals and alloys utilized are getting more specialized and unique in their composition. This in turn leads to an increase in the importance of the so-called high-tech metals [1]. Many such valuable elements are only produced as a by-product of another carrier metal in the absence of the specific minerals mined for their primary production. These minor, rare, valuable or special metals, however those technologically important hitchhikers are labelled, gained their importance in the last few decades [2]. As a result, they recently caught the attention of the recycling industry and as a consequence, industrial residues were landfilled for decades and by-products, as well as intermediate process streams, are still generated today without extracting these elements. A striking example of this is the iron precipitation "jarosite residue" from the hydrometallurgical zinc industry, which is the investigated material described in this paper. As a result of low zinc and lead contents, a targeted economic recycling of this material also has to take into account the present minor elements, such as indium and silver. In this context, a pyrometallurgical process is investigated which recovers zinc, indium and silver simultaneously as a dust product and the iron, as an alloy. The technology investigated is a reductive vaporization step, exploiting the selective formation of volatile compounds especially of Indium and Silver by the addition of a chlorine carrier [3]. Therefore, the paper summarizes the fundamentals, such as morphology of jarosite and required pre-treatment of the material, to allow the formation of volatile indium- and silver-compounds.

References:
[1] Paschen P.: Heavy nonferrous metals in world economy over the last 50 years. World of Metallurgy - ERZMETALL, 60 (2007), 263-272.
[2] Reuter M.: Metal recycling. United Nations Environment Programme, Nairobi, Kenya (2013).
[3] Steinlechner S. and Antrekowitsch J.: Thermodynamic considerations for a pyrometallurgical extraction of indium and silver from a jarosite residue. Metals, 8 (2018) online Proceedings.